The present invention pertains to magnetic heads that are used as contact-type or floating-type structures with respect to magnetic recording media, such as floppy disks, hard disks, and the like. [The characterizing feature of the present invention is that a surface with fine irregularities, where only the tip of the protrusions at the surface of the bearing surface facing a magnetic recording medium of a sliding member comprising polycrystalline nonmagnetic ceramics is an almost a flat surface, is formed by chemical etching using an etching solution with a needed composition without altering the properties of the smooth surface of the core member that has been finished by polishing. The present invention presents a magnetic head and a production method of good productivity with which improvement of sliding performance with no damage to the magnetic recording medium is expected and the smooth surface of the core member is maintained and there is no deterioration of electromagnetic properties.]
In addition to floppy disks (FD) of conventional recording capacity, large-capacity, high-density floppy disks are now being used as a result of improved recording media and large-capacity floppy disks exceeding 100 MB are being developed.
The mirror finish of the bearing surface has been very important to electro-magnetic properties of contact-type magnetic heads used in FD drives in the past, but when used, there are problems in that there is an increase in the turning load of the recording medium, an adsorption phenomenon is seen, etc. In order to prevent this adsorption, etc.,(sticking), it is necessary to increase driving torque. However, the above-mentioned problems have become more obvious because low-torque motors are being used today to conserve electricity.
Polycrystalline nonmagnetic ceramics, such as CaOxe2x80x94TiO2 systems, AlTiC systems, MnOxe2x80x94NiO systems, CaTiO3xe2x80x94NiO systems, CaOxe2x80x94MgOxe2x80x94TiO2 systems, CaOxe2x80x94MgOxe2x80x94TiO2xe2x80x94SiO2 systems, CaOxe2x80x94MgOxe2x80x94TiO2xe2x80x94SiO2xe2x80x94Al2O3 systems, etc., are being used for the sliding member of magnetic heads today in order to improve electromagnetic properties in response to the increase in density.
Moreover, the bearing surface facing the disk of a floating-type magnetic head, which has a structure whereby the disk floats as it turns at high speed and is used in hard disk drives (HDD), etc., must have a mirror finish to a higher accuracy and its floating performance must be guaranteed. However, an adsorption phenomenon between the disk and the bearing surface of the magnetic head that come into contact when the drive stops, or so-called sliding performance problems, develop when the mirror finish is more perfect and as a result, the CSS properties of the magnetic head are diminished.
In short, if the bearing surface, which is the face of the magnetic head that faces the recording medium, is polished to a mirror finish to the point that the lapping residue layer produced by the previous process is all but completely removed, there will be problems with the above-mentioned adsorption, etc., on contact.
Various structures, such as a structure where a core member is inserted into the sliding member or a structure where the core member is attached to or buried in the sliding member, are used for the magnetic head. All conventional structures use the following 2 methods to prevent the above-mentioned problems with adsorption, etc., for the purpose of realizing both good electrical properties and sliding performance. That is, the method has been used whereby the bearing surface of the sliding member and the core member of a magnetic head that face the magnetic recording medium are simultaneously polished to such an extent that the above-mentioned adsorption does not occur when they are polished to a mirror finish, or only the bearing surface of the sliding member is roughed to a certain extent after the above-mentioned polishing to a mirror finish.
Moreover, Japanese Patent Publication No.04-34203 presents a method whereby once the bearing surface of a sliding member made from Mnxe2x80x94Zn ferrite or Nixe2x80x94Zn ferrite has been polished to a mirror finish, reactive ion etching is performed to obtain the desired rough surface. Furthermore, Japanese Patent Laid-Open No.02-276074 presents a method whereby after the sliding surface of a sliding member made of Mnxe2x80x94Zn ferrite has been given a mirror finish, reverse sputtering is performed to make pits that are 50 to 100 A deep. However, this means cannot be used on polycrystalline nonmagnetic ceramics materials, and the above-mentioned long procedure time and poor productivity are problems.
Japanese Patent Laid-open No.02-310869 presents a method whereby the bearing surface or a sliding member made from a magnetic ceramics such as Mnxe2x80x94Zn ferrite, Nixe2x80x94Zn ferrite, etc., is roughed with a hydrochloric acid etching solution. Since both the sliding member and the core member are roughed, there are problems with this method in that a lapping residue layer is made, there are defects and scratches made in the core junction, leading to deterioration of the magnetic properties, and it takes time to align the head at the core junction, resulting is poor productivity.
Furthermore, Japanese Patent Laid-open No.08-36852 presents a method whereby the bearing surface of the sliding member made from a non-magnetic ceramics such as CaTiO3 or AlTiC, etc., is treated with an aqueous etching solution comprising oxidizing agent and acid or oxidizing agent and alkali so that this bearing surface is roughed without simultaneously eroding the core member with a mirror finish.
A simple device is used and therefore productivity is good with the above-mentioned method of etching with an aqueous solution comprising an oxidizing agent and acid or oxidizing agent and alkali. However, since the bearing surface that faces the magnetic recording medium that is obtained has a rough surface with irregularities that have sharp peaks and deep crevices, the tip of these protrusions being the sharp peaks, there are problems in that the magnetic recording medium is easily damaged and improvement of good sliding properties without obtaining sufficient air flow is undesirable. In particular, there is a problem in that the etching solution, which consists of an aqueous solution comprising oxidizing agent and alkali, dissolves the nonmagnetic ceramics component, and etching performance therefore is easily saturated.
The purpose of the present invention is to provide a magnetic head with both good electro-magnetic properties and sliding performance. Moreover, another purpose of the present invention is to give the bearing surface facing the magnetic recording material a mirror finish until the lapping residue layer made by the previous processes can be all but completely removed and then to form a surface with fine irregularities at only the bearing surface facing the magnetic recording medium of the sliding member in order to make a fine air flow path altering the properties of the smooth surface of the above-mentioned core member that has been finished by polishing. Another purpose of the present invention is to present a magnetic head and a production method of excellent productivity with which improvement of sliding performance and improvement of magnetic properties can be realized because the surface with fine irregularities that has been formed will not damage the magnetic recording medium.
The inventors felt that it was necessary to have good air flow between the recording medium and magnetic head during sliding in order to improve sliding performance. They further felt that in order to realize this good air flow, it was necessary to improve the cross section shape in the direction of depth at the bearing surface of the sliding member. Consequently, they felt that although the tips of the protrusions forming the rough surface with irregularities of the sliding member of conventional heads are sharp peaks relative next to deep crevices with respect to the magnetic recording medium, the tips of these protrusions should be an almost flat surface.
The inventors performed various studies of etching solution compositions that would make it possible to form a surface with fine irregularities where the tips of the protrusions of the bearing surface of the sliding member are almost flat in order to form a fine air flow path, and as a result they discovered that etching properties vary between phases when the material is a mixture of at least 2 compound phases, such as a CaOxe2x80x94TiO2 polycrystalline nonmagnetic ceramics. The inventors performed further studies and found that the tips of the protrusions in the bearing surface of the sliding member will be sharp peaks if the etching solution is an aqueous solution comprising an oxidizing agent and an alkali, and the junction of the magnetic core is markedly corroded by an aqueous solution comprising an oxidizing agent and an acid, but the tips of the protrusions can be made an almost flat surface and the surface of the core member that has been finished by polishing is unaltered with an etching liquid consisting of an aqueous solution comprising oxidizing agent and acid and alkali.
The inventors discovered that since the problems of adsorption between the sliding member and the magnetic recording medium at the bearing surface, etc., can be solved by the above-mentioned etching of the present invention, it is possible to give the bearing surface even more of a mirror finish and to completely remove the lapping residue layer of the core member in order to improve the properties of the magnetic head.
That is, the present invention is characterized in that the bearing surface facing the magnetic recording medium of a sliding member consisting of poycrystalline nonmagnetic ceramics, particularly polycrystalline nonmagnetic ceramics made from at least 2 or more compound phases with different etching properties, is etched with an etching solution consisting of an aqueous solution comprising oxidizing agent and acid and alkali after this bearing surface is polished to a mirror finish together with the core member to such an extent that the lapping residue layer on the core member can be all but completely removed.
The present invention makes possible specific surface modification by the above-mentioned etching, that is, formation of a bearing surface made from a surface with fine irregularities where the tips of the protrusions in the sliding member are an almost flat surface, but retaining the mirror finish of the core member and the realization of good electro-magnetic properties and sliding performance.
The inventors performed further studies in order to efficiently perform the above-mentioned chemical etching and focused on the fact that etching is not simply a reaction between ceramics and each chemical, but rather several parallel reactions, feeling that promoting only the effective reaction and inhibiting the reactions that are unnecessary or have the opposite effect or disrupt the effective reaction system are indispensable to improving the chemical reaction rate of etching, minimizing fluctuations in the reaction and making the reaction stable.
Therefore, as a result of various studies of etching solution compositions, the inventors discovered that generating efficiency of the desired surface modification is improved and this etching reactions can be controlled when etching is performed using an etching solution, selected for a specific surface modification of a needed ceramics, that contains a required amount of chelating reagent and the cations that are generated during etching will be trapped in the solution (chelation).
Moreover, the inventors studied suitable ceramics in order to more efficiently make the tip of each protrusion of the rough surface with irregularities almost a flat surface using the fact that there is a difference in etching performance between the phases of the above-mentioned materials that are mixtures of at least 2 types of compound phases. As a result, they discovered that a ceramics that is a mixture of at least 2 compound phases with efficaciously different etching properties can be obtained and the desired magnetic head can be produced by controlling the mean grain particle diameter of each raw material, the diffusing component that will diffuse and the component to which the diffusing component will diffuse during pre-baking and sintering, as needed by means of production of ceramics by the powder metallurgy technique.
That is, the present invention is a method of producing a magnetic head, characterized in that by means of a production method that consists of conventional powder metallurgy means, that is, processes involving mixing, pre-baking, crushing, molding, sintering, etc., the nonmagnetic ceramics are made from such the starting powders, consisting of at least raw material A as a diffusing component that diffuses during heating and raw material B as a component to which the diffusing component will diffuse during heating, wherein the average grain particle diameter of raw material A is greater than that of raw material B, preferably greater by 2-fold or more, is made into a ceramics for sliding members of magnetic heads by powder metallurgy.